A process for hydrating an olefin, especially a lower olefin such as ethylene, propylene or butene, to prepare a corresponding alcohol such as ethanol, propanol or butanol, is industrially important as alcohol has applications in many areas of industry, science, medicine, and technology. In light of the recent developments in using ethanol as a fuel source, improved processes for producing alcohol has become even more desirable Various processes are known for the alcohol hydration reaction, but using a mineral acid such as sulfuric acid or phosphoric acid as a catalyst has been the most prevalent industrial method of production. In addition, isopropanol (isopropyl alcohol) is widely used today as a solvent, disinfectant and fuel additive. In the chemical industry it is a very useful intermediate in organic synthesis.
Typically, alcohols such as ethanol or isopropanol may be produced by hydrating olefins using a phosphoric acid supported on a silica gel. In this process, however, phosphoric acid supported on the silica gel may be eluted causing degradation of catalyst activity. Accordingly, it is necessary to perpetually add phosphoric acid. Therefore, problems arise in connection with the treatment of the discharged waste liquid and the corrosion of the material of equipment. Furthermore, a large quantity of energy is necessary for recovery of unreacted ethylene or separation and purification of the produced ethanol because the conversion of ethylene is low.
A liquid phase process using sulfuric acid has also been widely adopted for the hydration of propylene or butenes, industrially. However, in this process, a large quantity of energy is necessary for hydrolysis of a sulfuric acid ester once formed. Because of the concentration and regeneration of the diluted aqueous sulfuric acid solution, equipment may be violently corroded by the acid at high temperatures.
From equilibrium considerations, it is preferred that the hydration of olefins be carried out at a low temperature under a high pressure, and ordinarily, these reaction conditions provide high conversions of olefins to alcohols. However, it is necessary to obtain an industrially satisfactory rate of reaction, and practically, severe conditions of high temperatures and high pressures are adopted for obtaining such a high rate of reaction. For these reasons, it is desired to develop a highly active solid acid catalyst for the hydration of olefins, which is capable of reducing the consumption of energy and not causing corrosion of equipment or other trouble.
Attempts have been made to use solid catalysts for the hydration of olefins. For example, processes have been proposed using complex oxides composed of silica, alumina, zirconia, titanium oxide, molybdenum oxide and tungsten oxide, metal phosphates such as aluminum phosphate and zirconium phosphate, and crystalline aluminosilicates called “zeolites” such as mordenite and Y type zeolite. However, these catalysts possess a low activity and the activity is gradually degraded when the reaction is carried out at a high temperature.
As can be seen from the above discussion, previous methods rely on improving the catalysts used in the hydration reaction. Presently, little or no investigation has been done in improving mixing of the reactants e.g. olefins and water for improving and optimizing the reaction.
Consequently, there is a need for accelerated methods for making an alcohol by improving the mixing of olefins into the water phase.